chore: add Docker dev files and ignore .sql database dumps

Added Dockerfile.dev for backend and frontend, docker-compose.dev.yml
for local development. Added *.sql to .gitignore to prevent accidental
commit of database dumps.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/Dockerfile.dev

@@ -0,0 +1,10 @@
+FROM node:20-alpine
+
+WORKDIR /app
+
+COPY package*.json ./
+RUN npm ci
+
+EXPOSE 5173
+
+CMD [ "npm", "run", "dev", "--", "--host", "0.0.0.0" ]